Petrus¸elA., I. A. Rus, and S¸erbanM. A. “Fixed Points for Operators on Generalized Metric Spaces”. CUBO, A Mathematical Journal, Vol. 10, no. 4, Dec. 2008, pp. 45–66, https://revistas.ufro.cl/ojs/index.php/cubo/article/view/1487.